The present invention relates to catheter systems for delivering stents.
A type of endoprosthesis device, commonly referred to as a stent, may be placed or implanted within a vein, artery or other tubular body organ for treating occlusions, stenoses, or aneurysms of a vessel by reinforcing the wall of the vessel or by expanding the vessel. Stents have been used to treat dissections in blood vessel walls caused by balloon angioplasty of the coronary arteries as well as peripheral arteries and to improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Two randomized multicenter trials have recently shown a lower restenosis rate in stent treated coronary arteries compared with balloon angioplasty alone (Serruys, P W et al., New England Journal of Medicine 331: 489-495 (1994) and Fischman, D L et al. New England Journal of Medicine 331:496-501 (1994)). Stents have been successfully implanted in the urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others. The term xe2x80x9cstentxe2x80x9d as used in this Application is a device which is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.
One of the drawbacks of conventional stents is that they are generally produced in a straight tubular configuration. The use of such stents to treat diseased vessels at or near a bifurcation (branch point) of a vessel may create a risk of compromising the degree of patency of the main vessel and/or its branches, or the bifurcation point and also limits the ability to insert a branch stent into the side branch if the result of treatment of the main, or main, vessel is suboptimal. Suboptimal results may occur as a result of several mechanisms, such as displacing diseased tissue, plaque shifting, vessel spasm, dissection with or without intimal flaps, thrombosis, and embolism.
As described in related copending U.S. patent application Ser. No. 08/744,022 filed Nov. 4, 1996, now abandoned; Ser. No. 09/007,265 filed Jan. 14, 1998; Ser. No. 08/935,383 filed Sep. 23, 1997; and 60/088,301 filed Jun. 5, 1998; and PCT Patent Application Publication No. WO 99/00835 filed Jan. 14, 1998; systems have been developed for deploying a main stent in a main vessel at the intersection of a main vessel and a branch vessel with a branch stent extending into a branch vessel through a side opening in the main stent. Unfortunately, several difficulties exist when attempting to position such an arrangement of a main and branch stents at a vessel intersection.
For example, the insertion of separate guidewires into both the main vessel and the secondary vessel is required before positioning a main stent in a main vessel with a branch stent projecting through a side opening in the main stent into a branch vessel. Main and branch stents are then advanced over the separate guidewires which have been pre-guided one after another into the respective main and branch vessels, such that the main stent can be deployed within the main vessel and the branch stent can be deployed through the side opening in the main stent into the branch vessel. Unfortunately, when attempting to guide two such separate guidewires through the main vessel such that one enters the branch vessel, the two guidewires typically tend to wrap around one another and become entangled. Additionally, time and effort is required to individually position each of the two guidewires one after another.
An additional disadvantage of conventional stents is the difficulty in visualizing the stents during and after deployment, and in general, the fact that they are not readily imaged by low-cost and easy methods, such as x-ray or ultrasound imaging.
The present invention provides a stent delivery system which comprises a catheter with a flexible side sheath attached thereto. In a preferred aspect of the invention, the catheter is adapted to receive a first guidewire therethrough, and the flexible side sheath is adapted to receive a second guidewire therethrough.
As will be explained, an advantage of the present stent delivery system is that it may be used for deploying a main stent in a main vessel with a side opening in the main stent being aligned with the ostium of a branch vessel. In additional preferred aspects, a branch stent can also be deployed in the branch vessel with the branch stent passing through the side opening in the main stent.
Accordingly, the present invention also sets forth methods of positioning a main stent at a vessel bifurcation such that a side opening in the main stent is positioned at the ostium of a branch vessel. In preferred aspects, a main guidewire is first positioned in the main vessel such that a distal end of the main guidewire extends past the bifurcation. Thereafter, the stent delivery system, (comprising a catheter with an attached flexible side sheath), is advanced to a position proximate the bifurcation, wherein the catheter is advanced over the main guidewire, and wherein the main stent is positioned over the catheter. In preferred aspects, the flexible side sheath is positioned to pass through the interior of the main stent, (positioned over the distal end of the catheter), and out of the side opening in the main stent.
Thereafter, a branch guidewire is advanced through the flexible side sheath and into the branch vessel. To assist in guiding the second guidewire into the branch vessel, the flexible side sheath may preferably taper to a narrow distal end, which may be curved slightly outwardly.
Subsequently, the stent delivery system is advanced with the catheter advancing over the main guidewire while the flexible side sheath concurrently advances over the branch guidewire. In one aspect of the invention, the side opening in the main stent is positioned in alignment with the ostium of the branch vessel due solely to the presence of the branch guidewire extending from an interior of the main stent out through the side opening in the main stent and into the branch vessel.
In another more preferred aspect of the invention, however, the side opening in the main stent is positioned in alignment with the ostium of the branch vessel by viewing relative movement of radiopaque markers positioned on each of the catheter and the flexible side sheath. In this aspect of the invention, the relative marker movement indicates that a portion of the flexible side sheath which is positioned adjacent the side opening in the main stent is advancing into the ostium of the branch vessel, thereby indicating the position of the side opening of the main stent with respect to the ostium of the branch vessel. In this aspect of the invention, the flexible side sheath will deflect into the branch vessel as it is advanced over the second guidewire, (while the catheter itself moves distally along through the main vessel over the first guidewire).
Such relative movement of the radiopaque markers may be viewed as a rotation of a marker on the flexible side sheath with respect to a marker(s) on the catheter, or as a separation between the marker on the flexible side sheath with respect to a marker(s) on the catheter. In certain aspects, the marker on the flexible side sheath is positioned adjacent a marker on the catheter, such that the relative marker motion will be viewable in an image as a separation occurring between the two markers. In a preferred aspect of the invention, the relative movement of the markers on the catheter and flexible side sheath can be observed fluoroscopically as the markers are radiopaque and are preferably made of suitable materials including tungsten and gold.
In addition, a plurality of markers may be positioned on the catheter with a marker positioned at locations corresponding to each of the proximal and distal ends of the main stent. A medial marker may also be included, positioned halfway between the distal and proximal markers, for indicating the position of the side hole in the main stent, (which is preferably positioned halfway between the distal and proximal ends of the stent).
In additional aspects of the present invention, the main stent is deployed in the main vessel, (such as by an inflatable balloon at the distal end of the catheter). Thereafter, a branch stent may be advanced through the at least partially deployed main stent and positioned in the branch vessel. Preferably, the branch stent is advanced through the at least partially deployed main stent by a second catheter, which then deploys the branch stent in the branch vessel, (such as by an inflatable balloon at the distal end of the second catheter).
To deploy the branch stent, the delivery system, (comprising the catheter and attached flexible side sheath), may be removed leaving the two guidewires in place such that the second catheter can then be advanced over the second guidewire and into the branch vessel. As such, the second catheter can then be advanced over the second guide wire with its distal end extending into the branch vessel.
An advantage of the present stent delivery system is that it avoids having to separately position first and second guidewires within the respective main and branch vessels prior to deployment of the main and branch stents thereover. Rather, with the present invention, only a single guidewire needs to initially be placed within the main vessel, with the delivery system subsequently deploying both the main and branch stents thereover.
The main stent may optionally include outwardly expandable portions which can be expanded from an initial position which is flush with the cylindrical body of the stent to protrude outwardly from the side opening in the main stent, thereby anchoring into the walls of the branch vessel, holding the side opening in registry with the ostium of the branch vessel. In an exemplary aspect, the cylindrical body of the main stent has an even surface, with an expandable portion positioned within the side opening of the cylindrical body, such that it is flush with the cylindrical body prior to expansion.
In addition, the branch stent may optionally comprise a contacting portion at its proximal end to secure the proximal end of the branch stent to the side opening in the main stent. In an exemplary aspect, the contacting portion comprises a flared proximal end.
Applications of the present system include the cardiac, coronary, renal, peripheral vascular, gastrointestinal, pulmonary, urinary and neurovascular systems and the brain. Further advantages of the present stent delivery system are that it provides an improved stent delivery apparatus, which may deliver main and branch stents to: 1) completely cover the bifurcation point of bifurcation vessels; 2) be used to treat lesions in one branch of a bifurcation while preserving access to the other branch for future treatment; 3) allow for differential sizing of the stents in a bifurcated stent apparatus even after a main stent is implanted; 4) treat bifurcation lesions in a bifurcated vessel where the branch vessel extends from the side of the main vessel; and 5) be marked with, or at least partly constructed of, material which is imageable by commonly used intraluminal catheterization visualization techniques including but not limited to ultrasound or x-ray.